Type 15 frigate

HMS Relentless (F185) after her Type 15 conversion
Class overview
Operators:	Royal Navy  South African Navy
In service:	1951–1977
Completed:	23
Retired:	23
General characteristics
Displacement:	2,300 long tons (2,337 t) standard 2,700 long tons (2,743 t) full load
Length:	358 ft (109 m) o/a
Beam:	37 ft 9 in (11.51 m)
Draught:	14 ft 6 in (4.42 m)
Propulsion:	2 × Admiralty 3-drum boilers Steam turbines on 2 shafts 40,000 shp (30 MW)
Speed:	31 knots (57 km/h; 36 mph) (full load)
Complement:	174
Sensors and processing systems:	Radar Type 293Q target indication (later Type 993) Type 277Q surface search Type 974 navigation Type 262 fire control on director CRBF Type 1010 Cossor Mark 10 IFF Sonar: Type 174 search Type 162 target classification Type 170 attack
Armament:	1 × twin 4 in (102 mm) Mark 19 gun 1 × twin 40mm Bofors Mk.5 2 × Squid or Limbo Mark 10 anti-submarine mortars
Aviation facilities:	Flight deck on Grenville and Undaunted

The Type 15 frigate was a class of British anti-submarine frigates of the Royal Navy. They were conversions based on the hulls of World War II-era destroyers built to the standard War Emergency Programme "utility" design.

By 1945 the wartime "utility" vessels were obsolescent as destroyers due to their relatively small size and makeshift armament. Future construction would be based on ever larger vessels, such as the Battle class and Daring class. Rapid advances in German U-boat technology with the 17 knot Type XXI and 19 knot Type XXVI rendered even some of the most modern Royal Navy escorts obsolete. This technology was being put into production by the Soviet Navy in the form of the Whiskey class submarine. The Royal Navy began designing and constructing new fast anti-submarine frigates of the Type 12 and Type 14 design to counter this threat. However, it would be some time before these vessels could be brought into service and budget constraints limited the number of new hulls that could be constructed.

The solution to the problem lay in the 47 War Emergency Programme destroyers that remained in Royal Navy service, most of which were only a few years old and had seen little active service. Accordingly, plans were drawn up to convert these vessels into fast anti-submarine frigates incorporating as many lessons learned during wartime experience as possible. Ultimately, 23 of the utility destroyers were fully converted into Type 15 first-rate anti-submarine frigates, and a further ten were given limited conversions, and designated Type 16 frigates.